This invention relates to a flame retarding thermoplastic polyester composition reinforced by glass fibers. More specifically, this invention relates to a glass fiber reinforced flame retarding thermoplastic polyester composition which comprises (a) a thermoplastic polyester, (b) decabromodiphenylether and/or decabromodiphenyl and (c) antimony trioxide, and which possesses excellent durability for thermal degradation and improved coloring properties in shaped form.
Thermoplastic polyesters such as polyethylene terephthalate and polybutylene terephthalate have a variety of excellent physical properties. Especially polybutylene terephthalate has recently attracted considerable interest as a molding resin material, because of its excellent moldability.
Such polyesters have been used as engineering plastics for example as raw materials for mechanical parts of various machines, electrical equipment and parts of motor cars. Recently it has been strongly desired that those engineering plastics be provided with fire-proof properties, that is the flame retardancy, in addition to well-balanced ordinary physical and chemical properties. Nowadays, such properties are indispensable to provide in thermoplastic polyesters in order to enlarge their use as engineering plastics.
The thermoplastic polyesters generally have more excellent heat resistant properties than other engineering plastic resins, and they also have excellent durability for thermal degradation. For this reason they are expected to be the most suitable synthetic resins for use as the raw materials for electrical equipment and parts of motor cars, if they are given flame retarding properties without losing their well-balanced mechanical properties.
Since fiber reinforced thermoplastic polyesters are usually used at a temperature higher than 100.degree.C, it is strongly desired to give them excellent heat-resistance and flame retarding properties.
Heretofore flammable organic polymers have been made flame retardant by adding a flame retarding agent such as organic halogen compound, a phosphorus compound, a large amount of inorganic material or their combination.
Generally speaking, however, the flame retarding agents deteriorate the original physical properties of the base polymer, and therefore it is of importance to find a good combination of organic polymer and flame retarding agent. In respect of polyesters several methods have been proposed.
For example, Japanese Patent Publication (Kokai) No. 46-2086 discloses combined use of decabromodiphenyl and antimony trioxide as a flame retarding agent.
According to this method it is possible to give reduced flammability to a glass fiber reinforced polyester resin, but the polyester composition thus obtained is not satisfactory in durability for thermal degradation, which is an important physical property and is required for engineering plastics.
When a combination of a halogenated aromatic compound and antimony trioxide is used as a flame retarding agent, it has been believed that the best atomic ratio of halogen to antimony is about 3.
However a flame retarding polyester containing such a flame retarding agent does not have improved coloring properties in its shaped form because of using the halogenated aromatic compound and antimony trioxide in the ratio referred to hereinabove.
Thus, the object of the present invention is to provide a fiber reinforced flame retarding thermoplastic polyester composition having excellent durability for thermal degradation. Another object of the present invention is to provide a fiber reinforced and flame retarding thermoplastic polyester composition which is moldable to form a shaped article having improved coloring properties.